The present invention relates to a heat release device for use with a printed circuit board on which electrical components are mounted.
There are known various methods for release of heat generated in a printed circuit board on which electric components are mounted. In one example disclosed in Japanese Unexamined Patent Application Publication No. 2004-172459, a multilayer printed circuit board or multilayer board having upper, inner and lower conductive layers is housed in a closed casing. Holes are formed through the multilayer board at a position where an electric component is mounted on the board so that the heat generated in the electric component is transferred from the upper conductive layer through the holes to the inner and lower conductive layers of the board. The upper, inner and lower conductive layers of the board are thermally connected to a heat conductive terminal through which the heat is released out of the casing into the surrounding air.
In another example disclosed in Japanese Unexamined Patent Application Publication No. 2010-103371, a printed circuit board having thereon a heat generating component is housed in a casing. Heat is transferred from the heat generating component to the printed circuit board and then released to the casing through a press fit component that is press fit in the printed circuit board and also in contact with the casing.
There is known a multilayer printed circuit board the inner layer of which serves as a power layer. In such multilayer board, when a large current flows from the power layer to the electric component, for example, for driving an electric motor of a compressor, heat is generated in the power layer. Such heat is difficult to be released because the power layer is the inner layer of the multilayer board. If the heat has any influence on the operation of the electric component, the heat needs to be released out of the multilayer board.
Release of the heat generated in the power layer may be accomplished, for example, by combining two methods disclosed in the above-cited publications No. 2004-172459 and No. 2010-103371. Specifically, electrically connecting the power layer to the heat conductive terminal or to the press fit component provides efficient heat transfer and hence efficient heat release.
In such method, however, electromagnetic noise possibly affecting the operation of the electric component may be emitted from the heat conductive terminal or the press fit component electrically connected to the power layer.
The present invention is directed to providing a heat release device that allows release of the heat generated in the power layer of the multilayer board and also allows shielding the multilayer board against the electromagnetic noise occurring due to the heat release.